CONTINUITY OF THE GERM-PLASM, 



ETC. 



PREFACE. 



The ideas developed in this essay were first expressed 

 during the past winter in a lecture delivered to the students 

 of this University (Freiburg), and they were shortly afterwards 

 — in February and the beginning of March — written in their 

 present form. I mention this, because I might otherwise be 

 reproached for a somewhat partial use of the most recent 

 publications on related subjects. Thus I did not receive Oscar 

 Hertwig's paper — ' Contributions to the Theory of Heredity ' 

 (Zur Theorie der Vererbung), until after I had finished writing 

 my essay, and I could not therefore make as much use of it as 

 I should otherwise have done. Furthermore, the paper by 

 Kolliker on 'The Significance of the Nucleus in the Pheno- 

 mena of Heredity' (Die Bedeutung der Zellkerne fiir die 

 Vorgange der Vererbung), did not appear until after the com- 

 pletion of my manuscript. The essential treatment of the 

 subject would not, however, have been altered if I had received 

 the papers at an earlier date, for as far as the most important 

 point — the significance of the nucleus — is concerned, my views 

 are in accordance with those of both the above-named investi- 

 gators ; while the points upon which our views do not coincide 

 had already received attention in the manuscript. 



A. W. 



Freiburg, i. Breisgau, 



June ]6, 1885. 



